Amorphous solid dispersion (ASD) is a formulation strategy extensively used to enhance the bioavailability of poorly water soluble drugs. Despite this, they are limited by various factors such as limited drug loading, poor stability, drugexcipient miscibility and the choice of process platforms. In this work, we have developed a strategy for the manufacture of high drug loaded ASD (HDASD) using hot-melt extrusion (HME) based platform. Three drug-polymer combinations, indomethacin-Eudragit®E, naproxen-Eudragit®E and ibuprofen-Eudragit®E, were used as the model systems. The design spaces were predicted through Flory-Huggins based theory, and the selected HDASDs at pre-defined conditions were manufactured using HME and quench-cooled melt methods. These HDASD systems were also extensively characterised via small angle/wide angle x-ray scattering, differential scanning calorimetry, Infrared and Raman spectroscopy and atomic force microscopy. It was verified that HDASDs were successfully produced via HME platform at the pre-defined conditions, with maximum drug loadings of 0.65, 0.70 and 0.60 w/w for drug indomethacin, ibuprofen and naproxen respectively. Enhanced physical stability was further confirmed by high humidity (95%RH) storage stability studies. Through this work, we have demonstrated that by the implementation of predictive thermodynamic modelling, HDASD formulation design can be integrated into the HME process design to ensure the desired quality of the final dosage form.
Amorphous solid dispersion (ASD) is one of the most promising enabling formulations featuring significant water solubility and bioavailability enhancements for biopharmaceutical classification system (BCS) class II and IV drugs. An accurate thermodynamic understanding of the ASD should be established for the ease of development of stable formulation with desired product performances. In this study, we report a first experimental approach combined with classic Flory–Huggins (F–H) modelling to understand the performances of ASD across the entire temperature and drug composition range. At low temperature and drug loading, water (moisture) was induced into the system to increase the mobility and accelerate the amorphous drug-amorphous polymer phase separation (AAPS). The binodal line indicating the boundary between one phase and AAPS of felodipine, PVPK15 and water ternary system was successfully measured, and the corresponding F–H interaction parameters (χ) for FD-PVPK15 binary system were derived. By combining dissolution/melting depression with AAPS approach, the relationship between temperature and drug loading with χ (Φ, T) for FD-PVPK15 system was modelled across the entire range as χ = 1.72 − 852/T + 5.17·Φ − 7.85·Φ2. This empirical equation can provide better understanding and prediction for the miscibility and stability of drug-polymer ASD at all conditions.
The anisotropy field dispersion in both magnitude and direction has been investigated in Ni–Fe thin films through the frequency range of 2–100 Mc/sec using rf ferromagnetic resonance (FMR). Measurements were centered around the region of field values near Hk where the theory of Smit and Beljers predicts that resonance can be seen at these frequencies. The linewidth measurements as a function of frequency follow a linear relationship which is extrapolated to zero frequency to obtain magnitude dispersion. The slope of this line yields ferromagnetic damping parameters α0 in agreement with Rossing and Nelson. Angular dispersion measurements are obtained by extrapolating a linear relationship between apparent angular dispersion and frequency to zero frequency.
Magnitude and angular dispersion measured by ferromagnetic resonance have been compared with measurements of the same quantities using a vibrating sample magnetometer (VSM), and the results are generally in agreement.
In addition, the strain dependence of the FMR linewidth has been measured at 2.5 Mc/sec for strains up to 3.4×10−4. A small increase in linewidth with strain has been noted.
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